In a backlight module of a liquid crystal display device, multiple light-emitting diodes (LEDs) are provided as light sources. A driving voltage for each LED ranges from 3.0V to 3.3V, and a voltage of a driving circuit for the backlight module cannot exceed 31.5V. Therefore, in the case of more than 10 LEDs, it is necessary to connect no more than 10 LEDs in series first to obtain a series branch, and then to connect the obtained series branches in parallel, but in this case, the number of the LEDs is limited. For example, in the case of 17 or 22 LEDs, as the LEDs cannot be evenly distributed in respective branches, branches with different numbers of LEDs are not allowed to be connected in parallel.
Besides, in the backlight module, the LED and the pad themselves have a certain width, and it is required to guarantee a safe distance between adjacent pads. Under this condition, for a backlight module with a fixed size, when the number of LEDs is too large, the interval between the adjacent LEDs is too small, which is likely to cause overheating problem; when the number of LEDs is less, light is insufficient, which results in dark areas in the display panel; when the number of LEDs is appropriate, branches with different numbers of LEDs are not allowed to be connected in parallel.
Consequently, how to enable any number of LEDs to be connected in series in each of the branches of the backlight module becomes an urgent technical problem in the field.